After reading about the rumored split-screen feature for the (9.7-inch) iPad, I couldn't think of how to implement this function in a way to make it work as something different than the multitasking we're currently having (with the difference that you can directly see a preview of the second/other app).

"iOS 8 is likely to supercharge the functionality of Apple’s iPad with a new split-screen multitasking feature, according to sources with knowledge of the enhancement in development. These people say that the feature will allow iPad users to run and interact with two iPad applications at once. Up until now, each iPad application either developed by Apple or available on the App Store is only usable individually in a full-screen view."

To interact with the chosen app you'd have to tap it, like you would do on your desktop when having several windows open. How would you know which app is currently selected? If then tapping on the already selected app (by mistake) you would invoke the copy/paste pop-up or move the curser if currently in a writing app. With a bluetooth keyboard it'll get even more confusing – especially now that apps add more and more keyboard shortcuts.
This additional tapping around on the screen won't make it any different than it is now with the conventional multitasking – only that you'll see two apps at once.
And then there's this other thing. For now one thing that always was such a good feature about the iPad was the fact that the full-screen view was optimized for offering that laser-focused attention to what you're currently doing. Would you be willing to sacrifice that?

"The feature is said to be designed with the 9.7-inch iPad display in mind, and it is unclear if the feature will work on the smaller-screened iPad mini. The feature is said to work exclusively in landscape mode, which allows for increased screen space."

Rumors about bigger iPads and iPhones aren't a new thing, but thinking about a 9.7-inch iPad in landscape view, which would give you two 7-inch portrait split-screens is kind of weird. On the other hand converting this thinking to the iPad mini, the 7.9-inch landscape screen would give you two 5.7-inch portrait split-screens. Two quote Steve Jobs, "are you getting it?"
After hearing about bigger iPhones coming as 4.7-inch and 5.7-inch (a year ago – recently 5.5-inch) models for quite some time, this is the first time that these sizes would make sense. Talking about bigger devices, a 12.9-inch iPad could also be seen as two 7.9-inch portrait screens.

Here's one more though about the smaller screens/bigger devices. Imagine running an iPad app on a scaled screen that is now as big an iPhone app, or thinking with even bigger devices, running a desktop sized iPad app as two iPad mini sized apps. Thinking about the later situation it seems more reasonable, but having this huge device as a portable device doesn't seem so reasonable anymore. On the other hand, think about how people complained about how small the iPad mini screen is in relation to the iPad Air screen. Thinking further, how small will the screen now be with the iPad (mini) split in two again.

< sarcasm > On the path to trying to make these devices usable as real-work devices, it seems like it will be even harder to make real work possible on the iPad. < /sarcasm >